A powerful winter snowstorm traveling through the Northeast has grounded thousands of flights, canceled school and shut down highways.

The National Weather Service says the weather system causing gusting winds and frigid temperatures dumped 21 inches of snow just north of Boston and up to 18 inches in parts of New York state late Thursday.

U.S. airlines have canceled more than 2,300 flights nationwide and some school systems in New England and New York extended Christmas break.

Travelers Ron and Heather Krochuk (KRO-chuk) from Toronto, Canada, were stranded Thursday night at a Boston hotel after their flight got canceled and said they'd make the trip home Friday morning -- by car.